The present invention relates to an envelope control device for a piezoelectric buzzer wherein levels of voltages applied to the piezoelectric buzzer are changed with time for effective envelope control.
Among the compact electronic devices such as electronic watches and small electronic calculators, some have been conventionally developed which have, in addition to their original functions, other functions such as an alarm function for outputting an alarm sound or a function of outputting a tone. The alarm function is utilized for signalling the time by buzzing at a predetermined set time. The tone outputting function is utilized for confirmation of operated keys or as a simplified musical instrument by generating a musical tone of "C" when the key "1" among the ten keys is operated, a musical tone of "D" when the key "2" is operated, a tone of "E" when the key "3" is operated and so on. However, a piezoelectric buzzer can only provide extremely monotonous sounds of the same volume and has thus been defective in that it cannot provide aftersounds as in natural musical instruments.
It is an object of the present invention to provide an envelope control device for a piezoelectric buzzer wherein a plurality of different voltage levels are obtained to be selectively applied to both surfaces or electrodes of the piezoelectric buzzer for performing envelope control and providing output sounds similar to the natural sounds.
It is another object of the present invention to provide an envelope control device for a piezoelectric buzzer wherein the resistances of resistor components interposed between the piezoelectric buzzer and the voltage source are charged with time for performing envelope control and outputting natural-like output sounds.